Coronary Artery Bypass Graft


Article Author:
Bradlee Bachar


Article Editor:
Biagio Manna


Editors In Chief:
Melissa Max
Danyae Lee
Manouchkathe Cassagnol


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Kyle Blair
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Abbey Smiley
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Daniyal Ameen
Altif Muneeb
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
5/17/2019 10:03:09 PM

Introduction

Coronary artery bypass grafting (CABG) is a major surgical operation where atheromatous blockages in a patient’s coronary arteries are bypassed with harvested venous or arterial conduits. The bypass restores blood flow to the ischemic myocardium which, in turn, restores function, viability, and relieves anginal symptoms. Almost 400,000 CABG surgeries are performed each year making it the most commonly performed major surgical procedure, but surgical trends have decreased as the use of alternative options such as medical treatment and percutaneous coronary intervention (PCI) have increased.[1]

In general, on-pump and off-pump are the 2 types of CABG surgical procedures with the difference being the use of a cardiopulmonary bypass circuit and an arrested heart to operate during an on-pump CABG. The conduits used as bypass grafts are routinely the left internal mammary artery (LIMA) and the saphenous vein grafts (SVG) out of the lower extremities. Other conduits that may be grafted include the right internal mammary artery (RIMA), the radial artery, and the gastroepiploic artery. The type and location of the grafts depend on the patient’s anatomy and the location of the arteries that are occluded. Typically, the LIMA is grafted to the left anterior descending (LAD) artery, and the other conduits are used for the other occluded arteries.[2]

Anatomy

The myocardium of the heart is supplied by 2 major coronary arteries: the left main coronary artery and the right coronary artery (RCA). The left main coronary artery is usually a short segment that branches into the left anterior descending (LAD) artery and the circumflex artery. The LAD branches further into diagonal branches and the circumflex artery branches into obtuse marginal branches. The RCA branches into the posterior descending artery (PDA) and the marginal branches.

The coronary circulation can be divided into left-dominant, right-dominant, and co-dominant systems depending on which artery supplies the interventricular septum and PDA. In a left-dominant system, the PDA is supplied by the circumflex artery; whereas, in a right-dominant system, the PDA is supplied by the RCA. Co-dominant arterial supply has the PDA supplied by both the RCA and circumflex arteries simultaneously.

Blockages in any of the coronary arteries cause a corresponding defect in myocardial perfusion, ischemia and if unrepaired can lead to permanent infarct or damage to the myocardium.

Indications

CABG is generally recommended when there are high-grade blockages in any of the major coronary arteries and/or percutaneous coronary intervention (PCI) has failed to clear the blockages. Class 1 recommendations from the 2011 ACCF/AHA guidelines are as follows[2]:

  • Left main disease greater than 50%
  • Three-vessel coronary artery disease of greater than 70% with or without proximal LAD involvement
  • Two-vessel disease: LAD plus one other major artery
  • One or more significant stenosis greater than 70% in a patient with significant anginal symptoms despite maximal medical therapy
  • One vessel disease greater than 70% in a survivor of sudden cardiac death with ischemia-related ventricular tachycardia

Contraindications

Contraindications to CABG include patient refusal, coronary arteries incompatible with grafting, and the absence of viable myocardium to graft.

Equipment

The equipment necessary for this major surgical operation includes not only the equipment required for most other surgical procedures but also many specialized pieces of equipment, including the cardiopulmonary bypass machine with a heater-cooler device to warm and cool the blood.

Personnel

The operation is performed by a specialized cardiovascular surgical team with extensive training and experience with taking care of these complex patients. The team consists of the cardiothoracic surgeon and their assistants, anesthesiologists, nurses, surgical technicians, and perfusionists.

Preparation

In preparation for surgery, the patient will need several tests performed in addition to the coronary angiography that diagnosed the coronary artery disease. They will need laboratory tests completed such as complete blood count (CBC), metabolic panels including liver function tests, coagulation panels, and hemoglobin A1c. Other tests may be required including electrocardiogram (ECG), echocardiogram, carotid ultrasound, chest x-ray, and possibly a CT chest or vein mapping of the lower extremities.

Preoperative medications such as beta-blockers are most often continued throughout the perioperative period to prevent arrhythmias such as atrial fibrillation. Aspirin was previously withheld 5 to 7 days before surgery, but recently, it has been recommended to be started or continued preoperatively.

On admission to the hospital, the patient will have intravenous access started, and their medications and preoperative tests will be reviewed. The surgical sites will be trimmed of hair, and the patient will be given a chlorhexidine bath.

Technique

The procedure starts after the patient is in the operating room and attached to the standard monitors. An anesthesiologist may place an arterial line for invasive monitoring of the patient’s blood pressure before induction of general anesthesia. After general anesthesia is induced and the patient is intubated, a central line for venous access and a pulmonary artery catheter may be placed followed by insertion of a transesophageal echocardiography transducer. The patient is sterilely prepped and draped, and a time-out is performed before surgical incision. Median sternotomy is performed by the surgeon for preparation of takedown of the LIMA to use as a conduit. A trained assistant, usually a physician assistant, nurse first assistant, or another surgeon, simultaneously removes the saphenous vein from one or both legs using open or video-assisted techniques. After suitable conduits are acquired, the surgeon orders anticoagulation, most often heparin, given in preparation for cardiopulmonary bypass (CPB). The patient’s aorta and heart are centrally cannulated, and the tubing is attached to the cardiopulmonary bypass circuit. After starting CPB, the heart is arrested using high-potassium containing cardioplegia so the surgeon can anastomose the harvested conduits to the coronary arteries distal to the blockages. After the surgeon anastomoses the distal portions, the conduits are attached to new ostia created in the proximal aorta. Then the cardioplegia is washed out, the heart begins to contract, and the surgeon can check the grafts for both blood flow and competence as well as checking for bleeding from the anastomosis sites. After that, the chest is closed using sternal wires, and the patient is transferred to the intensive care unit for monitoring of hemodynamic stability and extubation.

Complications

The complications of CABG include stroke, wound infection, graft failure, renal failure, postoperative atrial fibrillation, and death.  The stroke rate of CABG has been reported at 1% to 2% depending on the characteristics of the patient and their risk factors for stroke including advanced age, prior stroke, aortic atherosclerosis, peripheral arterial disease, perioperative atrial fibrillation, and diabetes.[3]

Sternal wound infection rates are about 1% and are dependent on risk factors such as obesity, diabetes, chronic obstructive pulmonary disease (COPD), and prolonged duration of surgery.[2][4]

Saphenous vein graft (SVG) failure is most common within 30 days of operation and is dependent on several factors including vein size and excessive length, distal runoff and slow flow, and hypercoagulability and thrombosis. Rates of SVG failure up to 25% have been seen with repeat angiography after CABG.[2] Alternatively, arterial grafts such as the left internal mammary artery (LIMA) and radial arterial grafts remain patent longer and have patency rates exceeding 90% at 10 years.[2]

Postoperative renal dysfunction rates after CABG range from 2% to 3%, with 1% requiring dialysis. Risk factors are multifactorial but include preoperative renal disease, advanced age, diabetes, type of surgery, LV dysfunction, and shock. No medications have been definitively shown to reduce the rates of CABG-induced renal dysfunction, but there may be an advantage of off-pump CABG over on-pump CABG.[2][5]

Atrial fibrillation within the first 5 days after CABG is relatively common with rates of 20% to 50% and is associated with increased morbidity with a higher risk of embolic stroke postoperatively as well as increased mortality. Preoperative treatment with beta-blockers and possibly amiodarone has been shown to be the most effective way to reduce the incidence of postoperative atrial fibrillation.[2]

The risk of perioperative death after CABG is dependent on co-morbidities, the urgency of the surgery, and the case-volume of the center where the operation takes place, ranging from 1% to 2%.[2]

Clinical Significance

CABG is an important major surgical procedure helping prevent major morbidity in a patient’s life by relieving anginal symptoms and improving quality of life. Appropriately selected patients receiving CABG have increased survival benefits compared to those receiving medical therapy or PCI alone.[3] 

Enhancing Healthcare Team Outcomes

Coronary artery bypass grafting requires a large, well-trained, and experienced team to help decrease the morbidity and mortality of the procedure and improve outcomes.  Studies have shown that improving communication, collaboration, and teamwork between team members can help to improve outcomes and increase patient safety.[6]


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Coronary Artery Bypass Graft - Questions

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A 65-year-old male with a history of diabetes mellitus type 2, hypertension, and hyperlipidemia presents with substernal chest pain radiating to the left jaw. The coronary catheterization reveals 95% LAD, 80% circumflex, and 85% RCA occlusion for which coronary artery bypass surgery was scheduled. During surgery, the left internal mammary artery of the left chest was harvested. After an uneventful surgery, a postoperative chest x-ray showed an elevated left hemidiaphragm. Which of the following nerve was injured during the left internal mammary artery harvesting?



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A 69-year-old extremely obese female with a history of uncontrolled diabetes mellitus type 2, hypertension, chronic kidney disease, peripheral vascular disease, and mild COPD presents for coronary artery bypass grafting surgery after a non-ST elevation myocardial infarction. Her postoperative recovery was complicated by a return to the operating room for surgical control of bleeding and uncontrolled coagulopathy. She remained intubated and mechanically ventilated for 36 hours after which she was successfully weaned from the ventilator and extubated to Bipap. Which of the patient's factors places her at the highest risk for sternal wound infection after bilateral mammary usage?



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Atherosclerosis after coronary artery bypass grafting (CABG) is a progressive event. It occurs most rapidly at which location?



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A 62-year-old male undergoes a difficult 3 vessel CABG, including a LIMA to LAD, SVG to a very small calcified PDA and SVG to OM. Postoperatively, the patient has low blood pressure, and the electrocardiogram shows an inferior wall myocardial infarction. His hemodynamics improve with inotropic support, but he continues to have hypoxia. His chest x-ray is unremarkable, and a V/Q scan is negative. Which of the following is the next best test to determine the diagnosis?



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The right gastroepiploic artery most frequently is used to bypass which of the following?



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Under which of the following circumstances should coronary artery bypass grafting be considered?



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A 76-year-old male with a history of hypertension and hyperlipidemia presents for coronary catheterization following an abnormal exercise stress test. The coronary catheterization shows left main coronary artery disease of 30%, left anterior descending 95%, circumflex 80%, first obtuse marginal 75%, diagonal 80%, and the distal RCA 30%. Class I recommendations for coronary artery bypass graft surgery for this patient include which of the following?



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A 62 year old female with a long history of smoking presents with chest pain. Work up reveals that she has severe coronary disease and needs a bypass. Her medical history reveals that she has left breast cancer followed by reconstruction with the transverse rectus abdominis flap. Which of the following conduits will not be used in her for her bypass?



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After coronary artery bypass, which agent is most effective for long-term survival?



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Which of these arterial graft is usually used as a free graft for coronary bypass?



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What is true regarding the use of a second internal mammary artery during coronary artery bypass surgery?



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When a vein is grafted to a non-critical coronary artery, what will be the likely outcome?



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A 66-year-old smoker is about to undergo a 3-vessel bypass. He would like to know if this is a curative procedure. You tell him that atherosclerosis does occur after coronary artery bypass and is a progressive event. At what site does this atherosclerosis usually occur?



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What is the most effective secondary prophylaxis after coronary artery bypass?



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A patient with cardiogenic shock has an intra-aortic balloon pump inserted. Transthoracic echocardiogram reveals an akinetic lateral wall. Dobutamine echo shows an increase in regional wall thickness. An angiogram shows a 90% lesion in proximal left anterior descending and 70% lesion in ostial circumflex. The cardiologist also described a patent mammary. What is the best treatment for this patient?



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A 67-year-old had a cardiac catheterization revealing a 95% lesion in the posterior descending artery (PDA), 60% in the obtuse marginal and a 75% lesion in the left anterior descending (LAD). A thallium scan revealed a fixed deficit in the inferior wall distribution. For which of the following is the patient taken to the operating room for revascularization?



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A 65-year-old man who is postoperative day 6 after a coronary artery bypass grafting (CABG) and is taking clopidogrel and aspirin presented to the emergency department with diaphoresis, generalized weakness, pre-syncopal episode, and right upper quadrant pain of the abdomen. His blood pressure was found to be 78/42 mmHg and heart rate 112 beats/min. Examination showed a hematoma expanding across the right upper quadrant and epigastric region of his abdomen. The site was tender to palpation with mild guarding but no rebound tenderness. The remaining physical examination was unremarkable. An abdominal ultrasound was performed, and he was found to have a pseudoaneurysm of his superior epigastric artery measuring 6 cm by 7 cm. Labs were significant for a hemoglobin of 7.7 grams/dL. He was administered IV fluids, and blood was transfused before being emergently taken back to the operating room for surgical exploration and right superior epigastric artery pseudoaneurysm repair. What is the likely cause of his pseudoaneurysm?



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A 66-year-old female with a history of diabetes mellitus, hypertension, and hyperlipidemia presents for three-vessel coronary artery bypass graft (CABG) surgery. Coronary angiography reveals left anterior descending (LAD) disease of 80%, circumflex 90%, second obtuse marginal 90% and posterior descending artery (PDA) 85%. A preoperative echocardiogram shows an ejection fraction of 65%, no wall motion abnormalities and no major valvular disease. The surgery was difficult due to small vessels making the vessel anastomosis difficult. In the cardiovascular intensive care unit, an hour after surgery, the patient becomes progressively hypotensive, requiring increasing titration of the inotropic medications. An urgent echocardiogram reveals akinesis of the inferior wall of the left ventricle. Which of the following vessels is most likely occluded in this patient?



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Coronary Artery Bypass Graft - References

References

Percutaneous coronary intervention versus coronary-artery bypass grafting for severe coronary artery disease., Serruys PW,Morice MC,Kappetein AP,Colombo A,Holmes DR,Mack MJ,Ståhle E,Feldman TE,van den Brand M,Bass EJ,Van Dyck N,Leadley K,Dawkins KD,Mohr FW,, The New England journal of medicine, 2009 Mar 5     [PubMed]
Coronary-Artery Bypass Grafting., Alexander JH,Smith PK,, The New England journal of medicine, 2016 Sep 8     [PubMed]
Reduction in incidence of deep sternal wound infections: random or real?, Matros E,Aranki SF,Bayer LR,McGurk S,Neuwalder J,Orgill DP,, The Journal of thoracic and cardiovascular surgery, 2010 Mar     [PubMed]
Off-pump coronary artery bypass surgery and acute kidney injury: a meta-analysis of randomized and observational studies., Nigwekar SU,Kandula P,Hix JK,Thakar CV,, American journal of kidney diseases : the official journal of the National Kidney Foundation, 2009 Sep     [PubMed]
2011 ACCF/AHA Guideline for Coronary Artery Bypass Graft Surgery: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines., Hillis LD,Smith PK,Anderson JL,Bittl JA,Bridges CR,Byrne JG,Cigarroa JE,Disesa VJ,Hiratzka LF,Hutter AM Jr,Jessen ME,Keeley EC,Lahey SJ,Lange RA,London MJ,Mack MJ,Patel MR,Puskas JD,Sabik JF,Selnes O,Shahian DM,Trost JC,Winniford MD,, Circulation, 2011 Dec 6     [PubMed]
Wahr JA,Prager RL,Abernathy JH 3rd,Martinez EA,Salas E,Seifert PC,Groom RC,Spiess BD,Searles BE,Sundt TM 3rd,Sanchez JA,Shappell SA,Culig MH,Lazzara EH,Fitzgerald DC,Thourani VH,Eghtesady P,Ikonomidis JS,England MR,Sellke FW,Nussmeier NA, Patient safety in the cardiac operating room: human factors and teamwork: a scientific statement from the American Heart Association. Circulation. 2013 Sep 3;     [PubMed]

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